Optical fiber cables are currently used in telecommunication applications for transmitting optical signals from one location to another. Oftentimes, it is desired to tap or splice into an optical fiber cable at a point other than at an end of an optical fiber cable to obtain access to an optical fiber in the cable.
A large number of optical fiber cables currently in use and being manufactured have a core formed from buffer tubes, each of which encloses a plurality of optical fibers. The buffer tubes typically are stranded longitudinally along the length of a central strength member using the well known technique of S-Z or alternate-hand stranding. Although the core without a jacket can be used as a cable, the core usually is enclosed by a plastic jacketing or sheath which obscures the positions on the strand where the S-Z reversals occur. At the S-Z reversal positions of the S-Z strand, the buffer tube lengths are longer than the length of the overlying elements of the cable, e.g., the jacket, which makes slack available in the tubes and the fibers contained in the tubes. As is known, this slack eases the process of making connections to the fibers in the cable at the point where the cable is entered.
It is known that markings applied on the outer jacket of an optical fiber cable, which includes S-Z stranded buffer tubes, at positions corresponding to the S-Z reversals in the strand are advantageous because the markings identify on the outside of the cable the positions of the S-Z reversals within the cable. See, for example, U.S. Pat. Nos. 4,828,352, 4,746,190 and 4,496,214, incorporated by reference herein. These markings, in effect, identify the slack points or S-Z reversal positions and guide one desiring access to a fiber in the cable to a point along the cable where access is more easily obtainable.
The current art, however, does not describe how to identify accurately the position of an S-Z reversal in a strand of S-Z stranded buffer tubes during optical fiber cable manufacture and, accordingly, how to place a mark accurately on jacketing applied on the strand of the cable at a position corresponding to an S-Z reversal of the strand contained within the cable, based on the identification of the S-Z reversals and as part of an integral and efficient cable manufacturing process performed along a conventional cabling line.
Therefore, there exists a need for a method and system for identifying the location of an S-Z reversal feature on a strand of S-Z stranded buffer tubes included in an optical fiber cable while the cable is advanced longitudinally along an optical fiber cable manufacturing line and for marking a covering, such as a jacket, applied to the strand at a position corresponding to the identified S-Z reversal, based on the identification of the S-Z reversal on the advancing cable.